Heat sensitive coating composition and copy sheet coated therewith



ec- Z, WOO H. H. BAUIVI 3,293,955

HEAT SENSITIVE COATING COMPOSITION AND COPY SHEET COATED THEREWITH Filed Dec. 12, 1965 TEMPERATURE-COLORABLE TEMPERATURE CAUSED BY COATING\ CONDUCTED HEAT V V A I comouc-rap HEAT 2 g I IIIIIIII I I I zz if U g 23 BAsE WEB OF COPY i EEX Q HEATED SHEET TRANSMITTING INFRA-RED BY ABSORBED INFRARED RADIATION IN ONE DIRECTION AND CONDUCTING HEAT IN ANOTHER RADIATION DIRECTION.

.fi I'NFRA-RED RADIATION SRCE I CONDUCTED HEAT THROUGH DATA CHARACTERS HEATED BY ABSORBED INFRA-RED RADIATION MASTER SHEET /MASTER SHEET W I 32 I I I III I I /I a LEASE WEB OF COPY SHEET \\-(IJIEI)PICEOD DATA TEMPERATURE-COLORABLE COATING PARTICLES OF METALLIC SALT OF AN ORGANIC ACID BASE WEB-PREFERABLY TRANSLUCENT TO MELTABLE PARTICLES INFRA-RED RADIATION AND HEAT A Z CONDUCTIVE-SUCH AS THIN PAPER or N NDOUNOBEN o SPIROPYRAN COMPOUND INVENTOR HENRY H. BAUIVI ms ATTORNEYS United States Patent 3,293,055 HEAT SENSITIVE COATING COMPOSITION AND COPY SHEET COATED THEREWITH Henry H. Baum, Dayton, Ohio, assignor to The National Cash Register Company, Dayton, Ohio, a corporation of Maryland Filed Dec. 12, 1963, Ser. No. 331,085 11 Claims. (Cl. 106-171) This invention relates to a thermo-colorable record copy sheet consisting of a base web, such as paper, coated with a normally substantially colorless coating that assumes a color where heated to temperatures used in ordinary thermographic printing, and to a composition for coating such a sheet.

The novel copy sheet is used in contact with a master sheet bearing data in infraredradiation-absorbing characters. Upon the two-sheet systems being generally subjected to infrared radiation, the characters become hot and cause a corresponding colored copy on the copy sheet.

This application is a continuation-in-part of copending United States patent application Serial No. 143,242, filed October 5, 1961, now abandoned in the name of Henry H. Baum.

In its preferred form, the novel copy sheet consists of a thin white sheet of paper coated on one side with a minimal amount of binder containing a profusion of minute interspersed solid particles or reactant materials being a mixture of at least one thermochromic indolinobenzospiropyran derivative having a melting point preferably in the range of 180 degrees Fahrenheit to 330 degrees Fahrenheit, and at least one metallic salt of an organic acid, whereby, upon the coatings being heated to the melting point of either the indolinobenzospiropyran material or the metallic salt, or both, a reaction occurs, forming an intensely-colored metallic complex or complexes.

The master sheet is placed in contact with the novel copy sheet, and the two-sheet system is exposed to radiation rich in infrared wave lengths. If a positive copy is to be made of the data on the master sheet, the heat induced in the characters is conducted through the base web of the master sheet or through the copy sheet, depending on the arrangement of the sheets, as will be explained, to cause the data to appear in color on the coated surface of the copy sheet.

In the preferred embodiment of the invention, the materials which immediately form the color when the coating is heated are a substituted thermochromic indolinobenzospiropyran compound having the molecular formula 1,3,3-trimethyl-4,7,8-trimethoxy [(Z'H-l benzopyran)- 2,2-indoline] and having the structure and calcium resinate or a mixture of calcium resinate and cobalt naphthenate, which materials develop a dark grayish-blue color on being heated to the melting point of the indolinobenzospiropyran compound, which is in the range of 220 degrees Fahrenheit to 225 degrees Fahrenheit.

In the preferred embodiment of the invention, calcium resinate and a smaller amount of cobalt naphthenate were used as the metallic salts, the combination giving the best results with respect to melting points and volatility ice of the active parts of the coating. In an actual pilot plant production of the preferred coating composition, the metallic salts first were combined together in a ball mill with a water dispersion of a polyvinyl alcohol binder, a surfactant, and water in the following amounts:

Mixture A: Grams Calcium resinate (5%6% by weight metal) 550.0

Cobalt naphthenate (5% metal by weight) 100.0

Polyvinyl alcohol-88% hydrolyzed and a viscosity of 3545 centipoises in a 4% water solution at 20 degrees centigrade as determined by the Hoeppler falling ball methodin a 7% aqueous solution 1,430.0 Nonionic surface active agent of the ditertiary acetylenic glycol type having a melting point of 37 degrees centigrade 3.5 Water 1,435.0

The ball milling was continued until a fine slurry was formed, which slurry then was combined with a slurry of the indolinobenzospiropyran-containing component made as follows. In a separate ball mill operation, the indolinobenzospiropyran compound of the coating composition was blended with a binder material, a surfactant, and water in the following amounts:

Mixture B: Grams 1,3,3-trimethyl-4,7,8 trimethoxy [(2'H-1'- benzopyran)-2,2 indoline] 330.0 Polyvinyl alcohol aqueous solution as specified for Mixture A 785.0 Nonionic surface active agent as specified for Mixture A 1.5

Water 815.0

Mixture A and Mixture B, when mixed together, form a coating composition of 5450.0 grams which may be used as is or as modified by the addition of 50 grams of a bluefluorescing whitener such as disodium-4,4-bis (4,6-dianilino-s-triazine-2-yl'amino)-2,2-stilbene disulfonate, commonly used as a fabric whitener.

The separate ball milling of Mixtures A and B is to forestall any premature coloration due to the possible reaction of the components which might be brought about by the ball milling of the materials together.

The quantities used in the preferred example may be enlarged upon for commercial batches.

As to the Water content of the composition, it may be varied as desired to meet the flow demands of the paper coater, paper of course being the preferred base web material, although other film-forming materials will do.

It is to be observed that the selection of binder and surfactant materials is not critical, and the person skilled in the paper-coating art will know of many binder substitutes for polyvinyl alcohol, such as methyl cellulose or hydroxy-ethyl cellulose, the criterion being that it be not too absorbent of infrared radiation.

The heart of the invention is the presence of minute solid particles of two reactants in close interspersed relation on a surface of a preferably white and noninfrared radiation-absorbent record material sheet, the reactants being so selected that at least one melts and reacts with the other at thermographic copy temperatures, the reaction product being colored and solid at room temperature, one of the reactants being an indolinobenzospiropyran compound and the other reactant being a metallic salt of an organic acid.

The color of the reaction product obtained in the thermographic operation is a composite of the color contribution from the indolinobenzospiropyran compound and the cation of the metallic salt. When a salt is used with a given spiropyran compound, the particular color contribution of the salt has been found to be primarily dependent on the cati-on, since essentially no difference in color is observed by varying the anion associated with any particular cation.

It is thus seen from the foregoing that the metallic salt cations play a dual role in the color-forming reaction. In one instance, the cation stabilizes the color produced in the thermographic printing operation by forming a complex or chelate with the spiropyran compound, and, in the next instance, such complex formation results in an ultimate color which incorporates a color contribution from the cation. The action of the cations is the same whether the spiropyran compound or the metallic salt has the lower melting point. In either case, all that is required to form a stable colored image on the copy sheet is that a concentration of metallic cations, at least divalent and suitable for complex formation, be present in a mobile or dissolved form, so as to react with available dispersed or liquid spiropyran material.

Each combination of spiropyran material and metallic cation provides its own characteristic color and color shade, examples of which combination are listed below in Table II.

It has also been found that the rate of color formation bears a direct relation to the melting point of the colorforming ingredients; the lower the melting point, the faster the rate of color formation. This is true whether the lower-melting material is metallic salt or the spiropyran material.

The coating composition is applied to the chosen surface in any of the conventional paper-coating methods of rolling, brushing, spraying, and the like, so that the dried film is of the order of 0.0005 inch in thickness.

The novel sheet is shown in the drawing in the two major forms of use with a master sheet, to give positive copies, together with a much-enlarged fragmentary crosssection of the novel copy sheet, showing in exaggerated diagrammatic form the disposition of its elements.

In the drawing:

FIG. 1 represents the copy sheet 21 with its uncoated back surface against a data-bearing surface of a master sheet 22. The infra-red radiation comes from above and passes through the temperature-colorable coating and the base web of the copy sheet to heat the data characters on the upper surface of the master sheet. The heat is conducted back through the base web of the copy sheet to effect a positive colored copy of the data in the coating of said copy sheet. It is apparent that the base web of the copy sheet should be thin, so that the energy of the applied radiation necessary to cause a copy of the data will be insufficient to heat the characters 23 on the bot tom of the master sheet to a temperature to interfere by heat conduction back through the master sheet and the base web of the copy sheet. Thus, a master sheet having data printed on both sides may be used with the novel copy sheet to reproduce the data on but one side. In this arrangement, the thickness, the translucence, and the heat conductance of the master sheet are not of first importance, as the applied radiation may be judiciously used to copy only that data in contact with the base web of the copy sheet. It is to be understood that FIG. 1 is diagrammatical as to dimensions and shows a flood-source of infrared radiation, whereas it is possible to move an infrared light source of spot or linear section over the copy paper, irradiating it in its various areas in sequence; or, on the other hand, the system of copy sheet and master sheet may be moved with respect to a stationary source of infrared radiation whose scope is less than the area of the sheets themselves.

FIG. 2 shows the arrangement of the two sheets 21 and 22, given a subscript a, where the copy sheet is on the bottom, with the temperature-colorable coating against the rear surface of the master sheet. The infrared radiation impinges directly against the data characters, and the induced heat passes through to cause corresponding coloration of the coating on the copy sheet. Here, the master sheet must pass the induced heat by conduction and should be relatively thin and of suitable heat-conducting material, Obviously, the system of FIG. 2 is not adapted to copy a master sheet bearing infrared-radiationabsorbing data on both sides. Also, in the system of FIG. 2, the heat and radiation transductance characteristics of the base web of the copy sheet are unimportant.

FIG. 3 is a diagrammatic section through a part of a copy sheet, showing the relative disposition of the base web, the coating, and the elements in the coating. The dimensions and the proportions of the elements are greatly out of proportion, as the particles of reactant are very small and are in close interspersed profusion, so that, in the preferred form, when the indolinobenzospiropyran compound particles melt, they make contact with the metallic salt particles. In the dried coating of the preferred embodiment, the binder constitutes about fifteen percent thereof, by weight.

Other compounds which may be substituted for the preferred 4, 7, 8' methoxy derivative of the parent compound 1,3,3-trimethyl [(2'H-1-benzopyran)-2,2-indoline] fall within the broad generic group of 1,3,3'-trimethyl [(2H-1'-benzopyran)-2,2 '-indoline] compounds which are substituted in at least the 8 position with an oxygen-containing group, preferably with a group selected from the class consisting of OCH -OCH H and NO The following table of substituent groups indicates a number of derivatives of the parent compound of the type within said broad generic group:

Table I Melting point Substituent: of derivative C. 8'-methoxy 123-5 8-ethoxy 83-5 1-ethyl-8'-methoxy 117-3 3-ethyl-8'-methoxy 96-8 1-amyl-8'-methoxy 72-7 1-phenyl-8-methoxy 161-4 3-phenyl-8'-methoxy -9 5-phenyl-8'-methoxy 167-71 5-phenyl-8'-ethoxy 119-22 7-phenyl-8'-methoxy 142-5 7-phenyl-8'-ethoxy 117-21 5-chloro-8'-methoxy -1 5-chloro-8-ethoxy 144-5 4,7-dichloro-8'-methoxy 90-100 5 ,8-dimethoxy -3 7,8'-dimethoxy 4,7 -dimethoxy-8-ethoxy 118-9 4,7-diethoxy-8-methoxy 104-6 5 ,7,8-trimethoxy 121-7 5,7-dimethoxy-8'-ethoxy 111-3 4,7-dimethyl-8'-methoxy 142-7 4,7-dimethyl-8'-ethoxy 82-4 5 -B-hydroxyethyl-8-methoxy 78-85 6'-chloro-8'-Me0 123-125 6-bromo-8-Me0 182-184 5',6'-dichloro-8'-EtO 125-126 1-ethyl*-6'-chloro-8'-Me0 95-96 1-ethyl-6'-bromo-8'-Me0 149-150 1-butyl-6'-chloro-8'-Me0 83-86 3-propyl-6'-chloro-8-MeO 121-123 1-phenyl-8'-EtO 134-136 1-phenyl-3-ethyl-8-Me0 111-114 1-phenyl-3-propyl-8'-Me0 145-147 1-phenyl-6-chloro-8'-Me0 153-155 1-phenyl-5',6'-dichloro-8'-EtO 121-122 3 -propyl-3-phenyl-8'-Me0 82 3-amyl-7-phenyl-8'-Me0 5,6-dichloro-8'-Me0 149-1 5 2 5,8'-de MeO-6'-chloro 155-157 7,8-di MeO-6'-chloro 104-106 4,7,8'-tri M'EO 104-106 5 Table IContinued Melting point Substituent: of derivative C.

6'-nitro-8'-Me0 166-168 6'-MeO-8'-nitro 116-117 4,6,8'-tri MeO 132-133 5-ch1oro-8-Et0 126-127 4,7,6'-tri chloro-8Me0 121-127 5,8'-di MeO-6'-bromo 125 5'-bromo-8'-Me0 183-185 5'-chloro-8-Me0 160-161 The preferred compound, as well as other indlin0 benzospiropyran compounds, are made by previously disclosed methods; for example, the method disclosed in The Journal of the American Chemical Society, 81, 5605 (1959), which discloses that the general method-for making this class of compounds consists essentially of condensing equimolar amounts of a salicylaldehyde compound and a Z-met-hylene-1,3,3-trimethylindoline compound, both materials being selected so as to provide the desired substituent groups at desired positions on the condensation reaction products; the methods disclosed in United States Patents Nos. 2,953,454 and 3,100,778; the conventional methods disclosed in Wizinger and Wenning, Helvetia Chimica Acta, 23, 247 (1940); and methods which are obvious modifications over those cited above and which differ thereover primarily in the use of specific condensation reactants which yield desired indolinobenzospiropyran compounds with the desired substituent group orientation; i.e., at desired ring positions.

The following examples are set forth merely to illustrate the preparative technique for making compounds of the class disclosed above. For this purpose, the details of preparing certain specified compounds of this class appear directly below:

EXAMPLE I The 4,7,8-trimeth0xy derivative.-One mole of 2,5- dimethoxyaniline, one mole of acetoin, and four moles of zinc chloride are placed in a two-liter flask and heated to 160 degrees centigrade for one hour. The reaction mixture is cooled, washed several times with water, and extracted with ether. The ether is evaporated off and distilled at 153 degrees centigrade/0.8 min. of Hg to give 0.85 mole of 2,3-dimethyl-4,7-dimethoxyindole.

T-he indole (0.85 mole) thus obtained is methylated by being heated at 120 degrees for five hours in 100 ml. of methanol with 2.55 moles of methyl iodide in a twoliter autoclave. The solid thus obtained is washed with acetone, decomposed with base, extracted with ether, and distilled at 142 degrees centigrade/ 1.5-2.0 mm. of Hg to give 0.4 mole or 4,7-dimethoxy-1,3,3-trimethyl-2- methyleneindoline.

To one mole of 4,7-dimethoxy-1,3,3-trimethyl-2-methyleneindoline in 200 ml. of ethanol is added one mole of 3-methoxysal:icylaldehyde (Tiemann, Koppe, Ber. 14, 2021 (1881)). The mixture is refluxed for two hours, filtered while hot, cooled, and filtered a second time. The precipitate is recrystallized from ethanol to give 0.93 mole of white powder, melting point 105 to 106 degrees centigrade.

EXAMPLE II The 6'-chlor0-8'-methoxy derivative.A solution of one IITlOlC of 3-methoxysalicyladehyde (Tiemann, Koppe, Ber. 14, 2021 (1881)) in 700 ml. of glacial acetic acid is bubbled with chlorine, the temperature of the solution being held below 20 degrees centigrade, until a yellow precipitate separates. The precipitate is recrystallized from ethanol to give 0.40 mole of -chloro-3-rnethoxysalicylaldehyde with a melting point of 117 to 118 degrees centigrade.

To 0.4 mole of 1,3,3-trimethyl-2-methyleneindoline in 100 ml. of ethanol is added 0.4 mole of 5-c-hloro-3-methoxysalicylaldehyde. The mixture is refluxed for two 6 hours, filtered hot, cooled, and filtered again to give 0.35 mole of white powder with a melting point of 125 to 126 degrees centigrade.

EXAMPLE III The 1 phenyl-8'-meth0xy derivative.To one mole of 1-phenyl-3,3,-dimethyl 2 methyleneindoline (Brunner, Ber. 31, 1943 (1898)) in 200 ml. of ethanol is added one mole of 3-methoxysalicylaldehyde (Tiemann, Koppe, Ber. 14, 2021 (1881) The mixture is refluxed for two hours, filtered hot, cooled, and filtered a second time. The precipitate is recrystallized from ethanol to give 0.90 mole of White crystals, melting point 163 to 164 degrees centigrade.

EXAMPLE V The 1-is0amyl-8-meth0xy derivative.One mole of l-isoamylaniline, one mole of acetoin, and 4 moles of zinc chloride are placed in a two-liter flask and heated to 160 degrees centigrade for one hour. The reaction mixture is cooled, washed several ti-mes with water, and extracted with ether. The ether is evaporated to give 0.80 mole of 1-isoamyl-2,3-di=methylindole.

0.8 mole of the indole is methylated in ml. of methanol with 1.6 moles of methyl iodide in a two-liter autoclave at degrees centigrade for five hours to provide the indole salt. The salt is Washed with acetone, decomposed with base, extracted with ether, and distilled at 98 to 107 degrees centigrade/0.7 mm. of Hg to give 0.56 mole of 1-isoamyl-3,3-dimethyl-2-tmethyleneindoline.

To V2 mole of 1-isoamyl-3,3-dimethyl-2-methyleneindoline in 200 ml. of ethanol is added /2 mole of 3- methoxysalicylaldehyde (Tiemann, Koppe, Ber. 14, 2021 (1881) The mixture is refluxed for two hours, filtered hot, cooled, and filtered a second time. The precipitate is recrystallized from ethanol to give 0.42 mole of white powder, melting point 76 to 69 degrees centigrade.

EXAMPLE VI The 8-etlz0xy derivative-To one mole of 1,3,3-trimethyl-Z-methyleneindoline (Brunner, Ber. 31, 1943 (1898)) in 200 ml. of ethanol is added one mole of 3- ethoxysalicylaldehyde (Davies, 1. Chem. Soc. 123 1587 (1923)). The mixture is refluxed for two hours, filtered hot, cooled, and filtered a second time. The precipitate is recrystallized from ethanol to give 0.85 mole of white crystals, melting point 83 to 85 degrees centigrade.

EXAMPLE VII The 5-chlor0-8-eth0xy derivative-To one mole of 5 chloro 1,3,3 trimethyl 2 methyleneindoline (Soc. Anon. Pour lInd. Chim. A Bale, Heinrich von Diesbach, Swiss 137,943, May 19, 1928) in 200 ml. of ethanol is added one mole of 3-ethoxysalicylaldel1yde (Davies, J. Chem. Soc. 123, 1587 (1923)). The mixture is refluxed for two hours, filtered hot, cooled, and filtered a second time. The precipitate is recrystallized from ethanol to give 0.80 mole of white powder, melting point 144 to 145 degrees centigrade.

Although resinates are preferred, the metallic salt anions may be, for example, acetates, naphthenates, stearates, ricinoleates, oleates, and the like, the latter two classes having exceptionally low melting points.

Generally, metallic salts suitable for use in the invention have a cation which is at least divalent and an organic anion including at least carbon, hydrogen, and oxygen and preferably so selected that the melting point of the salt ranges from a low of about 75 degrees centigrade to a high of about 250 degrees centigrade. Although metallic salts of the type just described are the preferred salts of the invention, any salt which can provide a multivalent cation in a milieu of spiropyran material and which has a melting point of at least 65 degrees centigrade may be used in the present invention.

Representative metallic salts useful in the invention and their melting points are listed below:

Melting point,

Compound: Degrees C. Aluminum Resonate 123-125 Calcium Resinate 205 Copper Resinate 145 Iron Resinate 154 (softens) Manganese Resinate 15 4 (softens) Lead Resinate 169 Zinc Resinate 205 Cobalt Naphthenate 77 Manganese Naphthenate 104 Calcium Ricinolate 85 Zinc Undecylenate 115 Barium Stearate 155460 Calcium Oleate 83-84 Calcium Stearate 179180 Lead Stearate 115 Magnesium Stearate 89 Zinc Oleate 70 Zinc Stearate 130 Zinc Acetate 237 The anions are of importance only in so far as they provide the desired melting point range of the selected metallic salt. As previously stated, the color-forming and complexing action of the cations is, at least within the melting point ranges set forth therein, essentially independent of the particular anions forming part of the metallic salts of the invention.

The colors produced by representative combinations of indolinobenzospiropyrans and metallic cations (the anion being the resinate in each instance) are shown in the following table:

TAB LE II Spiropyran Salt Cation Color of Print Derivative Calcium Blue-purple. Lead Do.

Magnesium Purple.

Manganese Blue-purple.

Orange-red.

Red-purple. Blue-purple.

G reen.

Dark blue. Blue-black. Red-purple. Blue. Brown. Purple-blue. Blue-purple.

Purple-blue. Green-blue.

Blue. Purple-blue. Blue.

D0. Purple. Purple-red. range-red. Purple. Blue. Gray-blue.

Some of the metallic salts tint the coating of the copy sheet slightly, as, for instance, while zinc resinate or acetate is white, the manganese salts are brown, the magnesium salts are light brown, the aluminum salts are light yellow, the lead salts are white, the copper salts are green, and the cobalt salts are purple, but, when used in small quantities in the coating, the colored salts are not of an objectionable nature, as their tinctorial effect is small.

While emphasis has been placed on the copying of data by infrared thermography, the novel copy sheet also is responsive to hot stylus writing, as commonly used in graph tracings of recording machines, or it may be used in conjunction with any other heat-recording instrumentality, such as hot type.

It will be apparent from the preferred embodiment that two metallic salts may be used in the coating, but such is not to be deemed limited to two. The invention also admits of the use of two or more of the indolinobenzospiropyran compounds in conjunction with one or more of the metallic salts, to give a mixed color effect, or a particular desired coloring temperature.

What is claimed is:

1. A record copy sheet consisting of a base web having on a surface thereof a temperature-colorable coating including a profusion of minute solid particles of two kinds in intimate interspersion, one kind of said particle being a metallic salt of an organic acid, the metallic cation being at least divalent and the melting point of the salt being at least 65 degrees centrigrade, and the other kind of particle being at least one indolinobenzospiropyran compound, said compound having an oxygen-containing radical at the 8' position selected from the group consisting of -NO OCH and OC H 2. The copy sheet of claim 1 in which the base web is paper.

3. The copy sheet of claim 1 in which the base web and the coating are substantially non-absorbent of infrared radiation.

4. The copy sheet of claim 1 in which the materials readily conduct heat.

5. The copy sheet of claim 1 which includes a mixture of metallic salts.

6. The copy sheet of claim 5 in which there is a mixture of particles of different indolinobenzospiropyran compounds.

7. The copy sheet of claim 1 in which there is a mixture of particles of different indolinobenzospiropyran compounds.

8. A coating composition dryable on a recording surface to form a temperature-colorable film, the coating consisting of an aqueous slurry of finely-ground entities of (a) a metallic salt of an organic acid, the metallic cation being at least divalent and the melting point of the salt being at least 65 degrees centigrade,

(b) particles of an indolinobenzospiropyran compound,

' said compound having an oxygen-containing radical at the 8 position selected from the group consisting of NO OCH and -OC H and (c) a water-soluble film-forming binder material.

9. The coating composition of claim 8 in which the slurry is approximately percent water.

10. The coating composition of claim 8 in which the solids constitute about 20 percent by weight thereof, approximately 50 percent of which is metallic salts, 30 percent indolinobenzospiropyran compound, and 15 percent binder.

11. The copy sheet of claim 1 wherein the metallic salt is calcium resinate and the indolinobenzospiropyran compound is 1,3,3-trimethyl-4,7,8'-trimethoxy [(2'H-1- benzopyran) -2,2'-indoline) (References on following page) References Cited by the Examiner UNITED STATES PATENTS Miller et a1. 117-36.8 Sprague et al. 1l736.8 Barman 117-36.8 Allen et a1 11736.8 Bakan et a1 117-36.8 Berman et a1. 11736.8

10 FOREIGN PATENTS 58,517 9/1960 Australia. 62,295 1/1961 Australia.

OTHER REFERENCES Barman, I. Am. Chem. 500., vol. 81, Nov. 5, 1959, pp. 5605-5608, 260319.

MURRAY KATZ, Primary Examiner. 

1. A RECORD COPY SHEET CONSISTING OF A BASE WEB HAVING ON A SURFACE THEREOF A TEMPERATURE-COLORABLE COATING INCLUDING A PROFUSION OF MINUTES SOLID PARTICLES OF TWO KINDS IN INTIMATE INTERSPERSION, ONE KING OF SAID PARTICLE BEING A METALLIC SALT OF AN ORGANIC ACID, THE METALLIC CATION BEING AT LEAST DIVALENT AND THE MELTING POINT OF THE SALT BEING AT LEAST 65 DEGREES CENTIGRADE, AND THE OTHER KIND OF PARTICLE BEING AT LEAST ONE INDOLINOBENZOSPIROPYAN COMPOUND, SAID COMPOUND HAVING AN OXYGEN-CONTAINING RADICAL AT THE 8'' POSITION SELECTED FROM THE GROUP CONSISTING OF -NO2,-OCHO3, AND -OC2H5. 